Expectations: initial implementation.
Disabled stub and infected assertions in IE9.

While it supports `Object.defineProperty()`, IE9 has a bug where
this in a getter on Number will always be 0 when using a primitive
(which must be 99.9% of numbers in JavaScript), thus making IE9 not
compatible with Stub and infected assertions.

Hopefully, IE10 is compatible (haven't tested thought).
MT_FORCE_LEGACY for bad Object.prototype infections.

Users may want to set MT_FORCE_LEGACY to allow minitest to infect
Object.prototype with methods directly, instead of using non
enumerable properties, which is safe but not compatible.

Of course, enabling MT_FORCE_LEGACY is dangerous, and will have side
effect, when dealing with libraries and for in loops that don't check
for hasOwnProperty, etc.

If you must support legacy browsers (IE < 10, FF < 4, etc.) you
should stick to assert/refute, expect and the stub method; ie.
everything that doesn't infect Object.prototype.
Merge branch 'master' into feature/expectations
README for expectations.
Merge branch 'master' into feature/expectations

Conflicts:
	README.md
Ignoring vendor directory and .env file.
Merge branch 'master' into feature/expectations

Conflicts:
	minitest.js
	test/index.html
Simplified grunt tasks.
Merge branch 'master' into feature/expectations
MT_NO_EXPECTATIONS variable to skip the infection.
Fixed matchers, thanks to some basic tests.
Simple test suite for expect().
Support for matchers in Internet Explorer 9.

IE9 supports Object.defineProperty but sadly has a bug with number
primitives, where this in a getter would always be 0, which makes
matchers useless when working with numbers in IE9.

But! We can (almost) safely extend Number.prototype with a method,
and thus use that method to overcome the above limitation.

And it works.
Updated built minitest.js